Geez man, you must know everything about everything.
Your answer is mostly true, but incomplete.
Many Google services do not work well in China. I can't use picasa or youtube. There are days when Gmail won't sync for several hours. I would assume there might be problems in other places where the government blocks or firewalls their internet connections.
While the Google services are blocked, it doesn't mean the entire internet is blocked. The Google services have to be configured right before entering China. Also check for a VPN provider.
Please note GMail is being "hacked" for a reason because expats in China, foreign journalists and Chinese "dissidents" use the service.
Also, Google Maps, despite the friction between Google and the Chinese gov, is the most used mapping service in China. Google has reapplied the Map's business license in China.
This is completely untrue. You can buy many unlocked phones online and use them in the US. You can also ask your carrier to unlock the phone (sometimes they will) for international travel.
Yes, many of those phones only are 3G 900 and 2100. Meaning you only get 2G GSM and EDGE on a US network. That means the phone isn't very useful in the US. You might like a phone that is both useful in the US and internationally.
Another thing. HTC phones are dual band 3G in particular. You get an unlocked HTC phone that works in Canada with 850 3G. Guess what, the second band is 1900. When you bring those phones to Asia and Europe, you're back in 2G GSM. Canadian spec phones being sold in online retailers, particular HTC, should be regaded on the same status as AT&T smartphones.
In other words, your 3G options are a set, either 900 and 2100, or 850 and 1900.
Now please note, Motorola is a bit more tricky. Some phones, like the Cliq 2, appear to have 2100 support as well. You have to dig their spec sheets to make sure.
If its Samsung, particularly from the Galaxy S line, they have a 2100 band. So their band pallets tend to be 1. 900, 1900 and 2100, and 2. 850, 1900 and 2100. Internationally you get #1. The Canadian and Latin American phones are #2.
To have a contract phone unlocked, you have to pay the ETF in general, and that will get you what you want at a cost. Usually people in business can afford that anyway. This case, the global CDMA phones from Verizon can also do the trick.
Furthermore, there are 2 versions of the Nexus S for GSM networks:
Tech Specs ? Nexus S
The OP wants model 1 (Quad band) for greatest compatibility. I'm not sure how easy it is to find that in the US.
The Nexus S for GSM comes with three models with the following 3G bands:
i9020T - 900, 1700, and 2100
i9020A - 850, 1900 and 2100
i9023 - 2100 or 900 and 2100
Can't find a good spec sheet for the i9023. This is the SLCD version found in India, Pakistan and Middle East countries. I believe this phone to have Arabic language support too.
In any case, the i9020T is what you find in Best Buy and works with T-Mobile 3G. The i9020A is what Negri sells and works on the AT&T network. This is also better known as having the white model. Both have 2100 Band 1.
The bottom line is that all three models will work with 2100, period.
Oh yeah, I actually tested this too.
I recommended the Nexus S because it is the easiest choice for a phone that has the 2100 band, yet works with a US carrier, and is unlocked out of the box. It is generally available in Best Buy, or online with Negri if you want the AT&T 3G compatible version.
Now if you really want to pay some big bucks, there is also the Samsung Galaxy SII. This has quad 3G band: 850, 900, 1900, and 2100. So it practically works 3G everywhere except for poor T-Mobile USA and Wind. Unlocked phones should be available online too. Just don't faint at the prices. Personally I would willingly pay a premium of over $200 for an unlocked SGSII over an unlocked Nexus S, honestly speaking. The SGSII is just amazing.
To the OP: You won't be able to control internet connection in other countries. Some people have success with VPN to escape blockades, so you could try that.
However, it has nothing to do with your phone. An iPhone, or any other smart phone, will have the same problems in that regard.
The single most important thing for you, OP, is will your phone have signal and work with the data service in the countries you travel to. You need to buy a phone (Android or otherwise) that can work on their networks. This means - check the band, and have an unlocked phone.
"Retweeted" for emphasis.
Here is a link:
UMTS frequency bands - Wikipedia, the free encyclopedia
Also, when the carrier is researched, one needs to find prepaid SIM and their APN aka Access Point Names.